Abstract

In February 2007, the U.S. Nuclear Regulatory Commission (NRC) issued Regulatory
Guide (RG) 1.129 Rev. 2, "Maintenance, Testing, and Replacement of Vented Lead-Acid
Storage Batteries for Nuclear Power Plants." In this RG, the NRC staff endorsed the Institute of
Electrical and Electronics Engineers (IEEE) Standard 450-2002, “Recommended Practice for
Maintenance, Testing, and Replacement of Vented Lead-Acid Batteries for Stationary
Applications." This standard provides the recommended practices, test schedules, and testing
procedures including recommended methods for determining a battery’s state-of-charge to
maintain permanently installed vented lead-acid storage batteries (typically of the lead-calcium
type) for their standby power applications. Previous versions of this standard suggested that
either float current or specific gravity could be used for determining the battery’s state-of-charge.
The NRC sponsored the research project described herein to validate the use of float charging
current as a measure of a battery’s state-of-charge for batteries that are used in the nuclear
industry. This report describes the approach taken, the specific activities performed to achieve
the objectives of this research effort, and the results achieved. It provides analysis of the data
and offers observations and recommendations for use by the NRC and its licensees.